地表条件对坡面产流的影响

本文将复杂地表条件对坡面流运动的影响概化为阻力的变化,运用运动波理论和修正的Green-Ampt入渗模型,建立了能够反映地表条件影响的坡面降雨入渗产流模型,数值结果与实验符合较好,运用该模型分析了植被、地形、坡长、坡度等地表条件对坡面产流过程的影响.

Laminar/Turbulent Plasma Jets Generated At Reduced Pressure

Laminar do plasma jets are attractive for precisely controlled plasma-material processing. The design of a novel non-transferred plasma torch enabled the switching between turbulent and laminar plasma flows by simply changing the plasma generation parameters. Images of the plasma flows generated at different conditions are presented.

A Modified Free Volume Model For Characterizing Of Rate Effect In Bulk Metallic Glasses

We investigate the plastic deformation and constitutive behaviour of bulk metallic glasses (BMGs). A dimensionless Deborah number De(ID) = t(r)/t(i) is proposed to characterize the rate effect in BMGs, where t(r) is the structural relaxing characteristic time of BMGs under shear load, t(i) is the macroscopic imposed characteristic time of applied stress or the characteristic time of macroscopic deformation. The results demonstrate that the modified free volume model can characterize the strain rate effect in BMGs effectively.

Gamma-ray induced color centers in Yb : YAG crystals grown by Czochralski method

20 at.% Yb:YAG single crystals have been grown by the CZ method and gamma-ray irradiation induced color centers and valence change of Fe3+ and Yb3+ ions in Yb:YAG have been studied. One significant 255 nm absorption band was observed in as-grown crystals and was attributed to Fe3+ ions. Two additional absorption (AA) bands located at 255 nm and 345 nm, respectively, were produced after gamma irradiation. The changes in the AA spectra after gamma irradiation and air annealing are mainly related to the charge exchange of the Fe3+, Fe2+, oxygen vacancies and F-type color centers. Analysis shows that the broad AA band is associated with Fe2+ ions and F-type color centers. The transition Yb3+ Yb2+ takes place as an effect of recharging of one of the Yb3+ ions from a pair in the process of gamma irradiation. (C) 2006 Elsevier Ltd. All rights reserved.

混合熔盐离子交换玻璃光波导的制备与特性研究

采用AgNO3和KNO3的混和熔盐作为离子源，系统地研究了K9玻璃离子交换过程中熔盐配比、交换时间和交换温度等工艺参数对波导性能的影响，得到离子交换玻璃波导折射率分布符合高斯函数形式，建立了波导特性与离子交换工艺参数间的联系。测试得到离子交换平板波导的传输损耗为0．45dB／cm，并利用离子交换技术在K9玻璃上制备了一种跑道形谐振腔滤波器，实现了滤波效应。

Influence of temperature and salinity fluctuations on propagation behaviour of partially coherent beams in oceanic turbulence

A theoretical study of the behaviour of partially coherent beams propagating through oceanic turbulence has been performed. Based on the previously developed knowledge of beam spreading of a partially coherent beam in the atmosphere and the spatial power spectrum of the refractive index of ocean water, we study the normalized root-mean-square width of a partially coherent beam on propagation through oceanic turbulence and its turbulence distance which may be a measure of turbulence resistance. Our analysis indicates that the behaviour of partially coherent beams on propagation may be described by the rate of dissipation of the mean-squared temperature chi(T) and that of salinity chi(S). In terms of a quantity w that defines the contributions of the temperature and salinity distributions to the distribution of the refractive index, chi(S) could be written as a function of chi(T) and w. Therefore, the behaviour of partially coherent beams on propagation can be characterized only by chi(T) for a given w. The results are shown for curved surfaces, from which one can see that partially coherent beams exhibit robust turbulence resistance when the water volume has a smaller chi(T).

用6个微卫星座位研究BMY牛和婆罗门牛的遗传多样性和群体遗传结构

对6个牛微卫星座位的遗传变异及多态性分析,以期了解BMY牛和婆罗门牛的群体遗传结构与育成情况.6个微卫星座位的多态信息含量为在0.524～0.752间,BMY牛、婆罗门牛两个群体的平均期望杂合度和观察杂合度值接近,分别为0.737 6和0.739 6,0 641 2和0.653 7,进入横交固定第二世代的BMY牛期望杂合度值较高,这与我们的育种进展相符.红安格斯的期望杂合度较低(0.460 9)接近日本和牛0.471,暗示红安格斯牛的同质性较高.

鸡血液中乙酰胆碱酯酶的提取研究

[目的]为了研究硫酸铵盐析法在乙酰胆碱酯酶分离纯化中的效果,从而利用乙酰胆碱酯酶的活性变化反映农药的污染情况。[方法]采用硫酸铵盐析和等电点区分的方法从鸡血中提取乙酰胆碱酯酶,并探讨其适宜的pH值范围。[结果]结果表明:pH值4.5左右大量的杂蛋白能被除去,可获得较高乙酰胆碱酯酶得率;采用饱和度为50%~60%的硫酸铵盐析效果较好,据此得出较佳的提取工艺。[结论]该研究结果为后续鸡血AChE的提取、分离、纯化等工作提供了相应的参考,同时为利用乙酰胆碱酯酶指示环境受有机磷和氨基甲酸酯类农药污染的后续研究和应

Low threshold current density 1.5 mu m strained-MQW laser by n-type modulation-doping

1.5 mu m. n-type modulation-doping InGaAsP/InGaAsP strained multiple quantum wells grown by low pressure metalorganic chemistry vapor decomposition technology is reported for the first time in the world. N-type modulation-doped lasers exhibit much lower threshold current densities than conventional lasers with undoped barrier layers. The lowest threshold current density we obtained was 1052.5 A/cm(2) for 1000 mu m long lasers with seven quantum wells. The estimated threshold current density for an infinite cavity length was 94.72A/cm(2)/well, reduced by 23.3% compared with undoped barrier lasers. The n-type modulation doping effects on the lasing characteristics in 1.5 mu m devices have been demonstrated.

个性化领域知识支持的用户主导需求获取方法

应用软件的需求获取与应用领域的特征密切相关,用户的参与日益受到重视,然而用户对系统的认识通常模糊且不完整,且对于多用户系统,需要拥有局部需求的多用户进行协同,才能得到完整、一致的需求.提出一种用户主导的需求获取方法,根据用户特征及其上下文环境,为用户进行需求定义提供个性化的领域知识支持,包括领域需求资产推荐和对多用户协同需求获取的建议.应用实例说明了该方法的可行性,且对于提高用户参与程度、改进领域知识重用效果,从而最终提高需求获取的质量具有积极意义.

Influence of 5A-Type Zeolite Powder on Tetrahydrofuran Hydrate Formation and Dissociation Process

Visual observations of tetrahydrofuran (THF) hydrate formation and dissociation processes with 5A-type zeolite powder were made at normal atmospheric conditions and below zero temperature by microscope. Results indicate that 5A-type zeolite powder can promote THF hydrate growth. At the same time, in the presence of 5A-type zeolite, agglomerated crystals and vein-like crystals of THF hydrate were also formed. SA-type zeolite powder increases the crystallization temperature and decreases the dissociation temperature. The particle size distribution of 5A-type zeolite powder influences THF hydrate formation and its dissociation characteristics significantly.